1. Field of the Invention
The present invention relates to air cooled equipment cabinets and more particularly to electronic equipment enclosures for housing sensitive and nonsensitive electronic components such as those used by telephone companies.
2. Description of the Prior Art
Electronic equipment cabinets are used to house electronic components, such as those mounted on circuit boards. Active components produce heat which must be dissipated from the cabinet for the circuitry to operate properly. Heat dissipation may accomplished by forcing outside ambient air through the housing by blowers or fans to remove the heat generated by the components. There is a problem with this technique, however, in that it exposes the components to airborne contaminants and uncontrolled humidity. Sensitive electronic components may not operate effectively under those conditions.
Sealed compartments are utilized to isolate the sensitive active components of the electronic circuitry from the outside ambient air. Fans mounted within the sealed compartments circulate the air. The heat generated by the active components is transferred to the ambient air via the exterior skin of the compartment. Natural or forced convection may be utilized to remove the heat therefrom.
A problem can result if the sealed electrical compartment is subject to direct sunlight. Sunlight subjects the compartment to solar loading which may severely limit heat dissipation therefrom of and even increase the temperature in the compartment.
In some instances, a jacket is placed around the sealed compartment to form a cooling air passage. Cooling air is forced into the jacket and through the cooling passage by blowers or fans. This increases the heat dissipation from the sealed compartment. The jacket also acts as a solar shield, blocking sunlight which might come into contact with the compartment.
Other air cooled electronic cabinets utilize a sealed compartment with one or more corrugated walls. The corrugation enlarges the surface area from which convection can occur, thus increasing heat dissipation.
In some electrical systems, and in particular telephone systems, nonsensitive passive components, such as fuses and lightning suppressors, are used in addition to sensitive active electrical components. Because these components are nonsensitive to an ordinary amount of airborne contaminants, they do not need to be isolated from the ambient air. In addition, telephone systems utilize a number of storage batteries which provide the DC current for the telephone system. Batteries are also nonsensitive and therefore do not require ambient air isolation. Additionally, batteries operate more effectively in an environment somewhat above ambient temperatures.